1. Field of the Invention
The embodiment discussed herein is related to an insulated busbar, an insulated busbar fabrication method, and an electronic apparatus.
2. Background of the Related Art
With electronic apparatus (such as power converters) in which semiconductor elements (such as power semiconductor elements) are used, insulated busbars may be used as wirings in order to accommodate a recent increase in the frequency of signals transmitted and received in the electronic apparatus.
A structure obtained by stacking plural plate conductors on each of which an insulating film is laminated with insulating plates (spacers) therebetween is known as one of insulated busbars. With such an insulated busbar (also referred to as a laminated busbar), as the distance between conductors diminishes, mutual inductance between them increases. As a result, inductance is reduced.
The recent progress of the development of SiC devices demands that electronic apparatus have high withstand voltages. In order to make the withstand voltage of an insulated busbar high, formerly the technique of pouring molten resin between plate conductors, preventing peeling from occurring at an adhesive interface between a conductor and the resin, and suppressing a partial discharge at a peeling part was proposed (see, for example, Japanese Laid-open Patent Publication No. 2010-274602 or No. 2010-274603). Furthermore, the technique of covering an end portion of a conductor with a thermosetting adhesive material to suppress the formation of a void (vacant space) between the conductor and an insulating film and to relax electric field concentration was proposed (see, for example, Japanese Patent No. 4618211).
However, the area of an insulated busbar used in, for example, a high power electric apparatus is large. Therefore, it is difficult to completely cover an end portion of a conductor with an insulating film for preventing the formation of a vacant space. As a result, an electric field concentrates in a vacant space and a partial discharge occurs. Repeated discharges cause unintended generation of gas or deterioration of an insulating material. Accordingly, power is not transmitted stably. A high withstand voltage is realized by increasing the thickness of an insulating material between conductors. However, this causes an increase in inductance and therefore is not desirable.
As has been described, there is room for improvement in the conventional techniques for making the withstand voltage of an insulated busbar high.